Properties of Synthetic Sapphire and Ruby
Generally properties
Chemical composition
Al2O3
Crystal structure Hexagonal
Purity 99.99%
Thermal properties Melting point 2050C
Softening point 1800C
Specific heat 0.18 cal/g.C (25C)
Thermal expansion
Parallel to C-axis: 6.710-6/C
Perpendicular to C-axis: 5.010-6/C
Thermal conductivity 0.09 cal/sec.cm.C (25C)
Mechanical properties Density 3.98--4.1 g/cm3
Hardness Mohs 9
Knoop 1800 face parallel to C-axis
2200 face perpendicular to C-axis
Modulus of elasticity 3.40--3.80106 kg/cm2
Compressive strength 21000 kg/cm2
Tensile strength 1900 kg/cm2
Bending Strength 4000 kg/cm2
Optical properties Index of refraction Parallel to C-axis: 1.769
Perpendicular to C-axis: 1.76
Index of infrared Transmission 83%
Electrical properties
Electrical resistance 1011 ohm/cm at 500C
106 ohm/cm at 1000C
103 ohm/cm at 2000C
Dielectric constant 7.5--10.5
Chemical properties Acids and alkalis attack 0 300C
Porosity 0